The Dynamic Endothelial Activation and Stress Index (EASIX) as a Predictor of Early Death and Long-Term Survival in Acute Promyelocytic Leukemia (APL): A Multicenter Study

<b>Background/Objectives:</b> Early death (ED) remains the primary barrier to long-term survival in acute promyelocytic leukemia (APL). Since current risk stratification models rely solely on static baseline parameters, they fail to capture the high biological volatility during the induction phase. We aimed to evaluate the prognostic value of the dynamic evolution of the endothelial activation and stress index (EASIX). <b>Materials and Methods:</b> This multicenter, retrospective study analyzed 131 newly diagnosed adult APL patients treated with the AIDA protocol. EASIX scores were calculated at admission (D0) and day 7 (D7). ROC, landmark, multivariable logistic and Cox regression analyses were performed to assess the impact of dynamic endothelial changes (ΔEASIX) on mortality and survival. <b>Results:</b> The ED rate was 25.2%. While baseline EASIX successfully predicted very early death (<7 days), dynamic assessment provided superior risk stratification. Worsening endothelial status (ΔEASIX > 0.35) was an independent predictor of early mortality (OR: 12.41, <i>p</i> = 0.007), inferior EFS (HR: 5.70, <i>p</i> = 0.004), and poor OS (HR: 3.69, <i>p</i> = 0.023). Landmark analysis stratified by the kinetic trajectory of ∆EASIX confirmed that patients above the optimal cut-off had significantly inferior 3-year EFS (56.3% vs. 77.8%, <i>p</i> = 0.041) and OS (59.5% vs. 78.0%, <i>p</i> = 0.026). <b>Conclusions:</b> To our knowledge, this is the first study to establish EASIX as a dynamic prognostic marker in APL. Our findings indicate that the "kinetic trajectory" of endothelial stress is a more accurate predictor of survival than static baseline assessment alone. While dynamic EASIX monitoring offers a valuable tool for real-time risk reclassification, these results require validation through prospective studies.